The present invention relates to a lock and key combination including                a lock having a cylindrical bore accommodating a rotatable key plug with a longitudinally extending key slot for receiving a key blade and at least one locking tumbler arranged in said key plug for engagement with a code pattern on said key blade, and        a key with said key blade,        said at least one locking tumbler having                    a key sensing portion, which is provided with two mutually spaced formations configured to engage with said code pattern on said key blade,            a body portion, which is rotatably journalled in a cavity in said key plug, and            a locking portion, which is formed on said body portion and is configured to cooperate with a locking mechanism adapted to lock said key plug against rotation unless a key blade with a correctly cut code pattern is inserted into the lock,                        said two mutually spaced formations on said key sensing portion being located so as to define a specific rotary position of said body portion upon inserting the key blade fully into the key slot, thereby releasing said locking mechanism and permitting rotation of said key plug in said cylindrical bore.        
The invention also relates to a lock forming part of such a lock and key combination, a key for opening such a lock, and a key blank for making such a key.
A lock and key combination of the kind referred to above is previously known from the patent specification U.S. Pat. No. 6,257,033 B1 (ZIV-AV). In this prior art combination each locking tumbler is constituted by a pin accommodated in a cylindrical cavity in the key plug, the pin being displaceable along and rotatable about the longitudinal axis of the cylindrical cavity. Each pin has an engagement end, located in the key slot of the key plug and being formed with two mutually spaced lugs or “engagement features”. These lugs will engage with associated depressions forming part of a code pattern on one side of a key blade.
The two depressions are separated by an intermediate ridge and are configured in such a way that the lugs of the associated pin will find their way down into the respective depression and cause the pin to rotate around its longitudinal axis. For this purpose, the code pattern on the side of the key includes a number of discrete depression pairs, these pairs being separated from each other and being distributed substantially in line with the cylindrical cavities and the associated pins, when the key is fully inserted into the key slot of the key plug of the lock.
Accordingly, when the key blade is fully inserted into the lock, the various locking pins will be rotated into predetermined rotational and axial positions so as to release the lock and permit rotation of the key plug in the cylindrical bore of the lock.